It has recently been shown in [1]}, on the basis of
magneto-hydrodynamical (MHD) simulations, that (i) the circumstellar rings appearing
to be comoving with the fastest-moving Wolf-Rayet stars are a trace of their very high
initial masses (\(\ge 35\)  to \(\sim 60\, \rm M_{\odot }\) ) inducing complex evolutionary
histories, and that (ii) their large-scale surroundings are main-sequence stellar
wind bow shocks fainter than the inner rings which became unobservable as the driving
star runs into diluted media [2]}.
This solved the apparent missing bow shock problem around some high-latitude,
Galactic, very fast-moving Wolf-Rayet stars like WR124, surrounded by its compact
gas nebula M1-67 [3]}, [4]}, [5]}, [6]} or WR71 [7]}, [8]}.
If we can now qualitatively explain the formation of quasi-spherical rings
around very fast-moving Wolf-Rayet stars, detailed observations of these
gas nebulae reveal much more complex structures whose formation
are far from being understood.
Which mechanisms distinguish between the production of ring-like shells
from ovoidal and/or other complex shapes ? What can we learn regarding
the past evolution of massive stars with nebulae of such morphologies ?
